Facebook revealed on Friday it received between 9,000 and 10,000 requests for user data from US authorities in the second half of last year, as it seeks to shield itself from a growing scandal.

Facebook revealed on Friday it received between 9,000 and 10,000 requests for user data from US authorities in the second half of last year, as it seeks to shield itself from a growing scandal.

The requests covered issues from child disappearances to petty crimes and terror threats and targeted between 18,000 and 19,000 accounts, the social networking site said, without revealing how often it complied with the requests.

Facebook "aggressively" protects its users' data, the company's general counsel Ted Ullyot said in a statement.

"We frequently reject such requests outright, or require the government to substantially scale down its requests, or simply give the government much less data than it has requested. And we respond only as required by law," he added.

Facebook is fighting an expanding public backlash after a government contractor revealed it was among nine Internet giants that turned over user data to the secret National Security Agency surveillance program PRISM.

The companies, which also include Apple, Google, Microsoft and Yahoo, have denied claims the NSA could directly access their servers. US authorities have said the program helped prevent terror attacks.

Facebook said it was able to report all US national security-related requests, which no company had previously been allowed to do, after pressing the government to release more details about the program.

But, for now, it said the government would only allow Facebook to provide the numbers in aggregate form and as a range.

"This is progress, but we're continuing to push for even more transparency, so that our users around the world can understand how infrequently we are asked to provide user data on national security grounds," Ullyot said.

Google asked the FBI and US Justice Department this week for permission to release numbers related to its handing over of data for the leaked surveillance programs, saying it has "nothing to hide."

The company's "transparency report" on government requests does not include national security requests under the Foreign Intelligence Surveillance Act that authorized PRISM.

Leaker Edward Snowden, who worked as a subcontractor handling computer networks for the NSA, is in Hong Kong, a semi-autonomous Chinese territory, where he has vowed to contest any possible extradition in court.

He also revealed the NSA's gathering of a huge trove of telephone metadata. US authorities said they could not mine the logs to target a specific user without authorization from a secret court.